1. Field of the Invention
The present invention relates to data communications, and more particularly to techniques of improving the configuration of the link between an end station and an intermediate device.
2. Description of the Related Art
Telephone subscribers are using the local loop for data communication in addition to voice. The local loop connects a telephone subscriber's customer premises equipment to the central office equipment at the network service provider. At the central office, the connection is routed to its destination, either directly or through other equipment in the network. New technologies are being employed to increase the bandwidth available over the local loop to allow subscribers, for example, to receive multimedia information on the Internet and the World Wide Web. One such technology is the xDSL family of technologies. xDSL are point-to-point public network access technologies that allow the transport of data, voice, and video over existing twisted-pair copper wire on the local loop between the subscriber and the network service provider. Asymmetric digital subscriber link (ADSL) is one such technology. In ADSL the transmission is asymmetric, allowing more transmission downstream from the network service provider to the subscriber than upstream from the customer to the network service provider. Thus, ADSL is advantageous for Internet use, video-on-demand, and remote local area (LAN) access, which typically require more transmission downstream (e.g., video images), than upstream (e.g., mouse click).
One protocol that may be used for transmission over the link is the point-to-point protocol (PPP). One version of the PPP is described in request for comments (RFC) 1661, published July 1994 by the Point-to-Point Protocol Working Group of the Internet Engineering Task Force. The communication over a link is specified by different protocols operating at different layers. ADSL is a lower layer protocol (at the physical layer) that may be used in conjunction with PPP. Other protocols, such as asynchronous transfer mode (ATM) or high level data link control (HDLC) may be used in a layer below the PPP and above the ADSL. So called HDLC-like framing is described in the RFC 1662 published July 1994 by the Point-to-Point Protocol Working Group of the Internet Engineering Task Force.
The point-to-point protocol, as it is defined, is used for transporting multi-protocol datagrams over point-to-point links. It consists of a specification for encapsulating multi-protocol datagrams, a link control protocol (LCP) for establishing, configuring and testing the datalink connection, and a family of network control protocols (NCPs) for establishing and configuring different network layer protocols. According to the PPP, network layer packets are referred to as datagrams. The datagrams are passed to the datalink layer in which they are encapsulated according to the point-to-point protocol in a packet having a packet header. The packet including the point-to-point protocol fields and the datagram is passed to a lower layer at which framing such as HDLC-like framing is appended to form a frame, the format received at the physical layer interface. Upon reception, the frame is stripped of its framing fields, and a packet is passed to the datalink layer. The packet is stripped of its control fields to produce a datagram. The datagram is passed to the network layer at which network layer headers and the like are processed.
PPP sessions are established between peers. In one typical environment, the peers include customer premises equipment, and a remote access server RAS operated by an Internet service provider ISP. The subscriber dials a telephone number to access the RAS of the Internet service provider. The PPP is utilized to establish the peer to peer connection from the customer premises equipment to the RAS.
Establishing a link over the local loop for use in PPP communications requires configuring the connection between the customer premises equipment and the central office according to common protocols. With information regarding the protocols used by the customer premises equipment, a craftsperson at the central office may configure the central office equipment accordingly. A craftsperson's time is expensive, and use of human intervention to configure the link may be subject to error. Additionally, after configuration, the subscriber may change to equipment using different protocols, thus making the current configuration inoperative.
As data traffic increases, the network service providers are logically or physically diverting the data traffic off of the voice networks into backbone networks more suited for data traffic or packet switched traffic. Thus, the central office switches are configured with a concentrator and multiplexer for data traffic which is split off of the voice traffic. Network service providers are beginning to deploy equipment that diverts calls destined for Internet service providers off of the voice switching network on to a dedicated backbone network for data transmission. This equipment terminates calls, extracts PPP data and encapsulates the data (for example, within logical connections in a tunnel). The tunnels refer to communication channels which operate according to tunneling protocols including the point-to-point tunneling protocol PPTP, the layer 2 forwarding protocol L2F, and a layer 2 tunneling protocol L2TP. These tunnels use the network service providers' backbone networks for connection to different Internet service providers. The logical connections within a tunnel are used as a means for multiplexing the data from several users into a single tunnel. In addition to tunneling, a variety of other techniques are utilized by the network service providers to manage the flow of data through their networks.
Lower layer protocols used on the link between the subscriber and the central office may be different from those used in the backbone network. For example, a link may be established between the customer premises equipment and the central office, where the link uses PPP, FUNI, and ADSL. The central office equipment may forward the call over a backbone network that uses ATM, a cell-based protocol, instead of being frame-based (frame-relay, for example). In order to forward the call over the cell-based backbone, the central office equipment will need to segment the FUNI frames into cells and transmit them via the ATM network. Such conversions may need to happen several times in the end-to-end data path.